< Superheater >
The photo shows the completed superheater. The boiler has three large flues,
therefore the superheater has three branches of the elements. The steam
from the regulator comes into the wet header, branches to the three flues,
returns and merges into the hot header, and goes to both sides' steam tubes.
The tube parts of the elements are made from copper tubes. Only the turning
part is made from stainless steel. The stainless steel part is brass-soldered,
while the other parts are silver-soldered.
The drawings show the section from a side. The outlet pipe from the regulator
goes through the regulator bush at the smokebox tubeplate. The tilt is
due to the boiler distortion. The superheater flange is fixed on the bush
with an o-ring. The o-ring is pressed in both radial and thrust directions,
so that the o-ring seals between the boiler inside, outside, and the tube
inside. The two circles show the sections of the wet header and the hot
header.
The turning part is made from a stainless steel round bar. Open two holes for the tubes, and drill a cross hole that will be closed with a plug.
The wet header and the hot header are made from 20 mm diameter copper tubes. The cross holes for the elements are drilled. Both ends of the tube are closed with brass plugs.
The tubes of the elements are bent sharply at the inlets and outlets of the headers. The tubes are annealed and bent with a homemade roller. Note a round bar in the tube in order to prevent distortion of the tube.
Nevertheless, the tube section was distorted. It is annealed again and corrected to a true circle by squeezing with a lathe collet.
The nipples, ferrules, and hollow nuts for the steam tubes are made from a brass round bar and a brass hexagonal bar. This time, only the nipples are utilized.
Silver solder the tubes of the elements on the wet header. Note the opposite ends of the tubes are gathered by flat bars.
It is not easy to get a small volume of a special material like brass solder. I got it from a Chinese webshop. It is almost the same as a general brass wire.
The stainless steel turning part is brass soldered on the tubes. The solder did not flow freely like silver solder.
This is a close-up of the completed superheater.
The brass soldering result looks no good. Therefore I execute the leak test for the brass soldering. Connect the superheater to the air compressor, sink the turning part in water, apply pressure, and confirm no babble is observed.
The superheater is mounted onto the boiler.
The superheater flange is screwed down onto the regulator bush. The four screws are arranged so that no part hides the screws in the front view, in order to replace the superheater assy from the smokebox door. Additionally, the two headers are arranged horizontally so that the flues and tubes could be cleaned up easily from the smokebox door.